Syntax Magazine

SYNTAX

Serving

The Timex-Sinclair Family
Of Personal Computers

A PUBLICATION OF THE HARVARD GROUP

VOL. 3 NO. 9

ISSN 0273-2696

SEPT., 1982

IN THIS ISSUE

8K Programs

Monthly Calendar . 5

Significant Figures

Subroutine . 16

Beginning Programming

ZX81 Math . 8

Classified Ads . 20

Dear Editor . 12

Hardware Review

ZX99 Tape Controller .. 19
Machine Code Programming

Testing Bits for

Branching . 19

Math Function Execution

Time . 16

Maximize Display File
for MC . 5

News, New Products .. 1 , 2 , 3
Program Corrections. .. ,17
Program Improvements ... 17
Report on the Spectrum.. 7
Software Review

Multifile . 9

Subscription Info . 23

TS1000 Test and Review.. 6

TV Sync Solution . .6

Users' Groups . 14

Index of Advertisers

Byte-Back . 9

Gladstone Electronics. .15

Memotech Corp . 4

Robin Products . 16

Softsync Inc . 3

Sinclair Research. .10, 11,

18

Zeta Software . 7

SQ, SYNTAX QUARTERLY, is
coming in November! All
SYNTAX subscribers get
the first issue free.

ATTENTION TS1000 OWNERS

All information about ZX81s in SYNTAX
also refers to Timex-Sinclair 1000s. The only
difference between the machines is that
TS1000S come with 2K RAM; ZX81s come with IK.

BASICARE OFFERS ZX81 MEGABYTE MEMORY DECODING

In late August BASICare of London intro¬
duced their Organic Micro system for ZX81s.

It consists of stackable modules, including a
memory mapping device to extend ZX81 address
space to IM bytes (129.95), 2K-64K RAM
(£19.95-64.95), 24 input/output lines
(£22.95), ultra-low power memory backed by
battery for nonvolatile program/data storage
(£32.95), and more. No US dealer now, but
you can buy direct, BASICare Microsystem
Ltd., 5 Dryden Ct., London SEll 4NH, UK.

ROSETTA STONE NOMINATIONS BEING ACCEPTED

Nominations are open for the 2nd annual
Rosetta Stone award, given for the best inde¬
pendent product (application, software pack¬
age, peripheral) for ZX/TS computers. Send
your nominee's name, address and phone number
to SYNTAX, RD 2 Box 457, Harvard, MA 01451
before 31 Dec 82. This year's prize, spon¬
sored by Mindware Inc. of Wayland, MA, will
be awarded by SYNTAX editors. Last year Dr.
Ian Logan won for his 8K ROM disassembly.

QSAVE CUTS SAVE/LOAD TIME

QSAVE, a 2-part package, drastically
cuts your ZX81 SAVE/LOAD time. The software
increases the baud rate, or data transfer, of
ZX81s to 4000, saving or loading 16K in 29
seconds. It also provides a program verify
to check for good save. The QSAVE hardware
is a 2-stage amplifier/filter. $30 US in¬
cludes postage. Personal Software Services,
112 Oliver St., Coventry UK CV6 5FE.

1

NEW PRODUCTS AND SERVICES

Ed. note; Unless specified, all
ZX81-related products should work
with Timex-Sinclair 1000 computers.

F/22 Press has cut the price of
their DARKSTAR darkroom program
complete package (DARKSTAR on tape
with documentation, ZX81, 16K RAM,
12" TV monitor, tape recorder) from
$550 to $475 (includes delivery in
continental US. F/22 Press, PO Box
141, Leonia, NJ 07605.

NIM Electronics plans to introduce
a ZX81 keyboard/enclosure kit in
late September. It consists of an
aluminum enclosure which mounts the
ZX81 PC board and a keyboard with
ZX81 legends on the sloping front
surface. Assembly time, according
to Ronald Kern, is about 20 min¬
utes, no soldering. Price; $150.
NIM Electronics, 1 Denise St.,
Parlin, NJ 08859, 201/721-0070.

Find over 600 ZX-TS products listed
in The Sinclair Computer Family
Sourcebook. Each listing gives a
description, prices, computer re¬
quirements and suppliers' names and
addresses. First revision, $6.95+
$1.25 postage, 93 pgs. New edi¬
tions are planned about every six
months, according to Randy Hecht.
Atlantic Computer Products, 5 Main
Plaza Suite 1424, United Virginia
Bank Building, Norfolk, VA 23510.

Eliminate heat-related problems
with the Power-Pack. It gives two
outputs; a fixed +5V at 1.2 amps
and a screwdriver-adjustable +6.5-
+15V. It also includes a push
button to clear the computer, a LED
power-on indicator and the connect¬
ing plug and cable. Full hookup
instructions included. The Power-
Pack is housed in a 5x4x3" aluminum
enclosure and the 120VAC-60Hz input
is fused for safety. Price is
$37.50 + $3.50 shipping. CA res.
add 6.5% MacSwan-Packaging Co.,

POB 4697, Downey, CA 90241.

Independent Sinclair service;
Tercentennial Technical repairs
Sinclair computers for a flat $35
rate plus shipping via UPS. Your
repair is guaranteed for 30 days.
According to manager Jack MacGrath,
average turnaround time is 2-3
days. Send your machine by UPS
with a description of the problem,
check or mo., and your name, ad¬
dress and telephone number.
Tercentennial Technical, 70
Tercentennial Dr., Billerica, MA
01821, 617/667-8272.

Get ready for the office pool —
PICK'EM predicts winning football
teams and point spreads in the NFL
on your 8K/16K Sinclair. On tape,
$9.95 plus $1.50 postage. Stuart
Software, 25381-G Alicia Pkway
Suite 316, Laguna Hills, CA 92653.

Norris Radio & Electronics have now
expanded their repair services to
the continental US (Jun.82). They
repair out of warranty ZX81s (kit
and assembled) and TS1000S for
$8. 50/hr plus parts. Turnaround
time is about 48 hours. Norris
Radio & Electronics, 144 Terry Dr.,
Slidell, LA 70458.

ZX Hardware Team of the ZX Users
Group of New York offers inexpen¬
sive 64K memories; $135 to club
members and $150 to nonmembers,
plus $5 postage. ZX Hardware Team,
Box 560, New York, NY 10005.

Winky Board cassette loader/dupli¬
cator interface includes LED level
monitor, earphone eavesdropper and
interference filter, plus circuits
for direct-copying any ZX/TS tape
(even programs that can't be listed
or saved). Only 1X1.5", Winky
Board needs no power or computer
mods, won't interfere with extra
memory. Info free. Assembled and
tested, $18 ppd. Kit, $12 ppd. PA
residents add 6%. Overseas add $2,
pay by international M.O. in US
dollars. G. Russell, RD 1 Box 539,
Centre Hall, PA 16828.

2

Add-a-Switch is an on/off switch
for your ZX81 or TS1000. It in¬
stalls instantly with no mods and
eliminates plug and jack failure.
Price: $14.95. Robert Downs, Lyon

Ware, 1520 S. Lyon, Santa Ana, CA
92705, 714/835-9512.

Fulcrum's ZX81 Loading Aid helps
load tapes first time. It plugs
between ZX81 and tape recorder,
using LED indicators to let you
correct recorder volume. Unit with
full instructions $21. Special
versions for ZX80s and ZX Spectrums
(specify when ordering). Fulcrum
also offers ZX/Spectrum Softwear —
short sleeved T-shirts with Sin¬
clair ZX81 or Spectrum lettering.
Red on black or white, S,M,L,XL
children's and adult's, $7. Im¬
proved Keyboard Bleeper gives short
Bleep with any keypress. Unit fits
under keyboard or ZX PC board, no
soldering. $19. Fulcrum Products,
Hillside, Steep Ln., Findon,
Worthing, West Sussex BN14 0UF.

RIP; QZX, the ZX newsletter for
amateur radio users, is ceasing
publication because its publisher
can no longer handle the load. If
you're interested in putting out
QZX, write to Marty Irons, K2MI, 46
Magic Circle, Goshen, NY, with "Re¬
placement for QZX" in big letters
on the envelope.

PROGRAMMING CONTEST

Computer Engineering Services
is sponsoring a Sinclair ZX pro¬
grammers' contest. First prize is
$150, 2nd $75, 3rd and 4th a year's
subscription to SYNTAX. Programs
must be original and written for
ZX80 with 8K ROM, ZX81 or TS1000,
in IK, 2K or 16K (specify config¬
uration). Rewrites from other
BASICS may be considered. Entry
deadline is 15 Oct 82. For com¬
plete rules and entry forms, write
Computer Engineering Services, The
Jarrett Company, PO Box 1222, Show
Low, AZ 85901.

ZX81 &TS1000 SOFTWARE

GRAPHICS KIT 16K

23 exciting machine code routines that give you control over your screen as never
before.

Draw/ Undraw - draws or deletes your multi-character shape which is defined in a REM
statement. You may define as many different shapes as you like and draw/undraw each at
will at whichever screen position you choose.

Border/ Unborder - Around the edges of your screen Edit lines can be used if required.
Your border is protected when foreground is on.

Foreground on /off - Protect existing characters on your screen. When on new shapes
will appear to slide behind and re-emerge from other shapes.

Reverse - converts all characters to their inverse video.

Fill - fills any number of lines you specify, starting at any line by your chosen character
PRINT POSITION CONTROLS

Up, down, left, right: alter your next print position in the direction indicated.

Editprint moves next print position to first edit line.

SCROLL facilities

Upscroll, Downscroll, Rightscroll, Leftscroll - scroll your screen in the direction
indicated.

Onscreen/offscreen - turns your screen on and off.

Search and Replace - will search the screen for every occurence of the character you
specify and replace it with new character.

Backgroun on /off - fills your screen with specified character. When foreground is on
existing information is unaffected and shapes will appear to pass in front of your
background without deleting it.

Square - draws a square or rectangle from your specified co-ordinate.

All these routines are in machine code for SUPER-FAST response. Simply load
GRAPHICS KIT, which repositions itself at the end of your RAM, and then your own
program (or key in a new one).

GRAPHICS KIT occupies slightly over 2K at the top of your 16K RAM and that includes
space to load the programmer’s TOOLKIT described below. On loading, it repositions
RAMTOP (see your ZX81 or TS-1000 manual) so it is protected from NEW and from being
over- written by your own program. ^

ibK ^14. 95

PROGRAMMERS TOOL KIT 1 6K

Line renumber - you state starting number and increment value. Free Space - tells you
how many free bytes you have left. Search and replace - changes every occurence of a
character as you require.

Tape routine - provides a system WAIT condition until a signal is received in the cassette
ear jack-has many uses!

Special Graphics routines - Hyper graphics mode - graphics as never seen on a ZX81
before. Fill - fills your, screen instantly with your specified character. Reverse - changes
each character on your screen to its inverse video. All these routines are written in
machine code!

Also includes all the above plus: GOTO’s and GOSUB’s included in line renumber.
Search for and list every line containing specified character.

An incredible achievment!! 16K $14.95

These 2 unique Toolkits are written as "compatible” and can therefore be loaded in
together. When loading The Programmer’s Toolkit on its own the user has first to enter a
poke code. However when used with the Graphics Kit, which is loaded first, the poke code
is not needed.

Buy both programs together for $25.00

WRITE FOR FREE CATALOG

□ Please send me copies of
GRAPHICS KIT @ $14.95 ea.

□ Please send me copies of
PROGRAMMERS TOOLKIT @ $14.95 ea.

Mastercard/VISA # _

Exp date _

Please add $1.50 shipping & handling
New York residents add sales tax.

SEND CHECK OR MONEY ORDER TO:

SaFTSYlMC^IIMC,

PO. Box 480, Murray Hill Station, New Mxk, N.Y 10156 (212) 685-2080

Foreign orders must be paid by International Money Order or
foreign draft in U.S. Dollars drawn on a New York bank.

NAME

ADDRESS.
CITY _

STATE/ZIP.

3

BEHIND EVERY
GOOD SINCLAIR
ISAMEMCFAK

If you own a Timex-Sinclair 1000 or
ZX81 computer, you should have a
Memopak behind it. From increased
memory to high resolution graphics,
Memotech has a Memopak to boost your
system’s capabilities. Every Memopak
peripheral comes in a black anodised
aluminum case and is designed to fit
together in “piggy back” fashion to enable
you to continue to add on and still keep an
integrated system look.

High Resolution Graphics

Printer Interface'^ Memopak RAM

Order at no risk

All Memotech products carry our 10
day money back guarantee. If you’re not
completely satisfied, return it in ten days
and we will give you a full refund.

And every Memotech product comes with a
six month warranty. Should anything be
defective with your Memopak, return it to
us and we will repair or replace it free of
charge. Dealer inquiries welcome. To order
any Memotech product call our toll-free
number 800/662-0949 or use the order
coupon.

l%lwitLn

CORPORATION

7550 West Yale Avenue
Denver, Colorado 80227
(303) 986-1516
TWX 910-320-2917

64KRAM

$179.95

109 95

16KRAM

59 95

Centronics Parallel Printer Interface 104,95

RS232 Printer Interface

13995

High Resolution Graphics

144.95

Shipping and handling

* All prices quoted in U.S. dollars
** Colorado residents please add sales tax
□ Check □ MasterCard □ Visa

Account No. _

Name

Memopak 64K RAM The 64K RAM extends the
memory of your Sinclair by 56K to a full 64K. It
is directly addressable, user transparent, is
neither switched nor paged and accepts such
basic command as 10 DIM A (9000). The
Memopak 64K turns your Sinclair into a
powerful computer suitable for business,
recreational and educational use. No additional
power supply is required.

Memopak 32K RAM The 32K RAM Memopak
offers your Sinclair a full 32K of directly
addressable RAM. Like the 64K Memopak, it is
neither switched nor paged and enables you to
execute sophisticated programs and store large
data bases. It is also fully compatible with
Sinclair’s or Memotech’s l6K R\M to give you a
full 48K of RAM.

Memopak 16K RAM The Memopak l6K RAM
provides an economical way to increase the
capabilities of your Sinclair. And at the same
time, it enables you to continue to add on other
features with its “piggy back” connectors. It is
compatible with the Sinclair l6K or a second
Memopak l6K or Memopak 32K to give 32K or
48K of RAM respectively.

Memopak High Resolution Graphics The
Memopak HRG contains a 2K EPROM monitor
and is fully programmable for high resolution
graphics. The HRG provides for up to 192 by 248
pixel resolution.

Memopak Printer Interface The memotech
centronics parallel or RS232 printer interface
paks enable your Sinclair to use a wide range of
compatible printers (major manufacturers’
printers available through Memotech at
significant savings). The resident software in the
units gives the ASCII set of characters. Both
Memopak printer interfaces provide lower case
character capabilities. The RS232 Interface is
also compatible with modems.

New products coming soon Memotech will
soon be introducing four new Sinclair
compatible products: a high quality, direct
connection keyboard, a digitizing tablet, a l6K
EPROM and a disk drive. Watch for our future
advertisements.

MONTHLY CALENDAR

This 8K/16K program displays a
calendar for any month in any par¬
ticular year. It uses equations
developed by Zeller, the astron¬
omer, to determine the day that the
desired month begins on. To run,
simply type in the program, press
RUN, and select the desired month
and year for the calendar. This
program accepts the data and deter¬
mines the name of the month (lines
1-210). Next the program deter¬
mines the number of days in the
requested month and checks for a
leap year (lines 240-420). Finally
the program displays the final
calendar. To display another
month, simply press RUN again and
enter the necessary information.
There are no special instructions
for exiting; the program does so
automatically.

Herb Cohen, Winchester, KY

i "

1 REH Cni-ENDER
S FRST

10 PRINT "ENTER fl TO

S© INPUT H

3© PRINT "ENTER VfeRR"

4.0 INPUT Y
SO" t-ET

7© LET HON=rf
Q0 LET YERRssY

i?i hiJ gJtlJ ="URNURRY
gf tSJ ="FEBRURRY

110 hU =”HRRCH

hiT g$ t4.3 ="npRXL

111 hi! g$«Si*"MRY

iSi ="-«UNE

iSg ^^t7>="vJULY

iRra ="HUGLfST

9©© g* =** OCTOBER

«ia L^ 9f J ="*^0^EHBER "

ail DIH R?i|f ^ “"OECEHBER "

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ill

V?Z? Y.^4. = INT ON£> V -ino!

iY^l©0) THEN L^ LeIpLI^®®
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^|10 IF H=i QR M=2 then LET M=M
^,320 IF H=13 OR H = 14. THEN LET Y

34.© LbT NUHrs C Ry*? — XNT 1

LET NUH=1NT (NUH^.:ijr ' ^ ^ '

let 3TRRT=NUH

START =7

FOR R=STRRT TO 4-2
LET A tPJ =DAY

l et DAV=& AY+1
next P

CLS

PRINT TAB 10; A$ (NON) ; "B" ; YE

35©
35©
37©
33©
3Q©
4.0©
4.x©
4.^©
4.3©
4.4.0
RR

SUN HDN TUE UED

’•^hR^7

45© PRINT
45© PRINT “

THU PRX SRT"

4.7© FOR R=© TO 5
4.5© FOR 0=rXi-R^T TO
^©0 CXC:=^-^R^T

TAB C4.

A<c.t=0 then goto 5S0

THEN PRINT TAB

53© IF A«C>>END THEN

54.0 PRINT TAB
S5© NEXT C
56© NEXT R
57© STOP
SYrTTACTIC SUM:

t4.*0C>

GOTO
A fC> ;

55©

issea .. SK

MAXIMIZE DISPLAY FILE FOR MC

I upgraded my ZX81 to 2K of
RAM. Lately I have been interested
in programming machine code dis¬
plays. The problem is that since
my machine has only 2K RAM it al¬
ways sets up a minimal display
file. (See ch.27 p.l29 in the
BASIC manual.) To do any kind of
MC display you cannot have a mini¬
mal display file. I used to use a
short routine that would PLOT a
line up the right side of the
screen. This "opened" the display
and allowed a MCD. This was slow
and tiresome to do.

I remembered the BASIC manual
states that if you had more memory
you could POKE RAMTOP lower than
3.25K to fool CLS into setting up a
minimal display file. So I figured
why not go the other way, that is,
POKE RAMTOP higher than 3.25K to
fool CLS into a full display. It
worked! I have used my computer for
a while this way and no crashes or
problems whatsoever.

The procedure for POKEing
RAMTOP is somewhat different than
the manual states: once you power

5

up, POKE 16389,78 and then CLS.

Wait for a moment and voila, cursor
and a full display. (To verify
this, try POKE 16520,6.)

Remember, a full display will
occupy 793 bytes of RAM. This may
be no good for IK machines. Also
if you execute a NEW you must re-
POKE RAMTOP to get a full display
again. You can switch between
minimal or full display file by
POKEing RAMTOP at any time during
programming. I use POKE 16389,72
for a minimal display and POKE
16389,78 for a full display.

John Guineau, Marlboro MA
TV SYNC SOLUTION

If your ZX81 display has dim
lines and horizontal distortion
moving up or down the screen, it's
not synchronizing with the TV hori¬
zontal sweep. A simple component
change on the Sinclair circuit
board will solve the problem.

Here's what's happening: The
ZX81 uses a 6.5 MHz ceramic filter
as the frequency-determining ele¬
ment in the oscillator (clock).

The filter is loaded with a 100 pF
capacitor (C6) to reduce the
frequency to about 6.3 MHz. When
the Sinclair Logic IC divides this
down, the TV horizontal sync
frequency (15750 Hz) is obtained.
The tolerances on both the ceramic
filter and the capacitor are large
enough to produce a sync frequency
that may be outside the lock-in
range of the TV horizontal sweep
circuit. If the sync frequency
produced by the computer is too
high, the lines move down; if too
low they move up. To correct the
situation and get stable lock, just
change the value of C6. To reduce
the frequency, increase C6. Tack-
solder small-value capacitors
across C6 on the bottom of the
circuit board. Start with a 10 pF.
Increase it until the lines disap¬
pear. Trim the leads on the final
capacitor to about 3/4 inch, insu¬

late them, permanently solder the
capacitor, and position it parallel
to the board. If the frequency is
low, you'll have to replace C6.
Substitute a 10-20 pF capacitor to
make the frequency too high, then
follow the preceding steps.

In my case, the horizontal
sync frequency was about 15600 Hz.

A new C6 value of 57 pF locked the
sync in solidly.

Larry Forman, Santa Barbara, CA
TSIOOO TEST AND REVIEW

Syntax bought a Timex-Sinclair
1000 and TS1016 (16K RAM pack) from
a discount house. (We have a par¬
tial list of Timex computer out¬
lets. If you can't find one, call
us.) The prices weren't discounted
— $99.95 for the computer and
$49.95 for the RAM.

Our TSIOOO performs flawless¬
ly, even running continuously for
24 hours. Our RAM pack developed
occasional crash problems after a
few hours. We saw symptoms such as
numeral 4 and graphic symbols on
the display followed by system
crash when we pressed BREAK, and
unrecoverable loss of display sync.
Another RAM brought by an acquaint¬
ance would not execute its startup
routine. Our RAM healed itself,
and has shown no problems for days.

Timex provides a 1-Amp power
pack with low ripple and heating.

With the TSIOOO comes a 3-
program starter tape. It loads
easily, but poorly introduces TS
capabilities. The programs are
Life (esoteric math simulation).
Maths (arithmetic test program) and
Averages (mean and median demo).

All run in IK RAM. Life crashes in
16K, and the directions should say
press X, not C, to clear.

Instructions (in minute type)
are unclear (for example, press
newline after each entry — key is
labeled ENTER). Tell friends who
buy TS machines to read the manual
before trying the starter tape.

6

A REPORT ON THE SPECTRUM

MEH 5 ZX81 16K. RRM MEEW !!

Sinclair's new color machine, the
Spectrum, has been available in the
UK for several months; no word when
it will cross the Atlantic. — AZ

The Spectrum is a ZX81 that
has been developed by adding a hi-
resolution display, color board,
improved cassette interface and
larger keyboard. These features
are available to ZX81 owners but
increase the cost considerably and
make the fragile ZX81 more diffi¬
cult to use. Now they are stand¬
ard, giving the Spectrum a robust¬
ness sorely lacking in earlier
Sinclair models.

Drawbacks? Again the keyboard.
Despite its improved nature, it is
still a small calculator type key¬
board and not for fast typing. And
the display has only 768 color
areas, clearly a compromise.

Comparing the operating sys¬
tems of the ZX81 and the Spectrum,

I find several fundamental changes.
No longer is the display produced
in software. The ULA is mainly
responsible for scanning the 6K of
memory (block 4000-57FFh) that
holds the bit pattern for the
memory-mapped display. This scan¬
ning is done between Z80 access
periods. The ULA also scans the
"attribute area." This 0.75K area
of RAM (block 5800-5AFFh) holds the
color information for the 768 char¬
acter areas of the display. Each
attribute byte can describe 1 of 8
"ink" colors, 1 of 8 "paper" col¬
ors, 1 of 2 brightness states and
flash-on or flash-off. The names
"ink" and "paper" are generally
considered "foreground" and "back¬
ground" on other machines. Over¬
all, the Spectrum has 16 colors if
you consider the bright colors
different from the normal colors.

No longer is the keyboard
scanning done in the display rou¬
tine. Now the maskable interrupt
system scans for key presses every
l/50th (UK) of a second and enters

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F 0 0 T B R 1... L. 1” 0 R E C R S T i£ Rl b y G S rfi i t h
Get this one QUICK a.s the data,
base is for the 82-83 season,.

S P e c i f y C 0 L. L. E G E o r P R 0 v e r s i ci ti „
Money Order 9et;ir.- rush del i'i.,'ery „

REVERSI by Peter Ulrich
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the appropriate value into the
system variable LAST_K.

No longer are the input/output
routines almost inaccessible. Now
the appropriate routine addresses
are available as "channel informa¬
tion," which is in effect a vector
table in RAM.

But what is the same?

The BASIC interpreter is vir¬
tually untouched. The new features
(multiple statement lines, multiple
INPUT lines, the provision of READ,
DATA, RESTORE and DEF FN); have just
been melded in. The floating-point
calculator is also much the same as
in the ZX81. But there is some
integral arithmetic and FOR-NEXT
loops using integers run 20% faster
than otherwise. The cassette for¬
mat is also the same insofar as
there are no parity bits or check¬
sums. But the new standard is most
impressive and allows for programs,
arrays and blocks of code.

Ian Logan, Skellingthorpe, UK

7

BEGINNING PROGRAMMING — ZX81 MATH

Computing newcomers often face new
terminology. This article expands
on bits, bytes and binary numbers
over the ZX81 and TS1000 manual.

An elementary understanding of
the mathematics involved with your
computer will help you get the most
enjoyment and use out of it. Your
computer is a digital machine, or
"number cruncher." When you press
a key, whether it is an alpha char¬
acter (letter), graphic symbol or
numeral, it is immediately con¬
verted to a numerical value. If
you hate math, don't quit yet —
we'll start at the beginning.

When we count up from 1, we
run out of single digits after 9.

So we go to double digits. The
number 10 means one ten and no
ones; 11 means one ten and one one,
and so on. You understand the
meaning of each digit by its posi¬
tion in the numeral.

Let's look at the numeral
6382, read six thousand three hun¬
dred and eighty-two. We can break
it down like this;

6382= (6*1000) +(3*100)+ (8*10)+ (2*1)
The number 1000 is the same as
10x10x10, or 10 cubed. It can be
written symbolically as 10^ (10
raised to the third power). The 3
in 10^ is called the exponent and
is written to the right and above
the number being raised. Since we
cannot enter an exponent this way
on the ZX81, the symbol ** (shifted
H) is used, eg., 10**3. We can now
write the equation for our number
using exponents;

6382=6*10^+3*102+8*101+2*10^

As you see, 10 raised to the zero
power equals 1. Try it on your
computer (PRINT 10**0). So our
usual number system consists of 10
digits and is based on 10 raised to
a power, said to be base 10. We
call this system DECIMAL, or more
correctly, DECIMAL NOTATION.

Your computer consists of
thousands of transistors used as

8

electronic switches. A switch has
only two positions, on and off. So
the number system used to express
what's happening within the compu¬
ter is quite different from the
decimal notation we are used to.
Because a switch has only two
states, we need only two digits, 0
and 1, and our number system will
be base 2. This system is called
BINARY. A Binary digiT is called a
bit. Let's take the 4-bit binary
number 1101 and express it in ex¬
ponential form as we did to the
decimal number. Remember that a
binary number is in base 2.

1101= (1*2^ )+(1*22)+( 0*2^) +(1*2®)

= 1*8 + 1*4 + 0*2 + 1*1

= 8 + 4 + 0 + l

= 13 in decimal

By putting a binary number in ex¬
ponential form we can convert it to
its decimal equivalent. But how do
you go from decimal to binary? If
you don't have a computer program
to do it for you, you can use the
method of succesive subtraction of
powers of two. The name is the
worst part. Let's take the decimal
number 13. Start by finding the
largest power of 2 that will divide
into 13. Then divide the remainder
by the next lower power of 2;

2^=16 13/16 Too Big . ^ «

2'^ 2^ 2"^ 2^

2^=8 13/8=1 remainder 5 1
2^=4 5/4=1 remainder 1 1

2;:=2 1/2=0 remainder 1 0

2®=1 1/1=1 1
So decimal 13= binary 1101.

The Z80 microprocessor chip
used in the ZX81 and TS1000 is an
8-bit device, meaninvg that it can
handle 8 binary digits of data at
one time. This grouping of 8 bits
is called a byte. So we can say
that each memory location in our
computer is a byte wide. When we
express a byte in binary notation,
it is customary to write all 8
bits, even though there are leading
zeros. For example, binary 1 is
written as 00000001.

William Wentz, Rio Rancho, NM

SOFTWARE REVIEW

Product: MULTIFILE — A Data Storage

System
Price: $29.95

ROM/RAM required?: 8K/16K
Printed listing?: No
Program listable?: Yes
Screen prompts?: Yes
Easy to Load?: OK
Display?: Very good
From: Gladstone Electronics, 1585

Kenmore Ave., Buffalo, NY 14217

Multifile arrives with the
program tape, 10 pages of photo¬
copied instructions, 3 blank tapes,
and a 4-tape cassette album. The
instructions are lengthy, but
thorough. You should have no prob¬
lems operating the program or
understanding its structure after
reading these pages carefully.

Multifile is menu-driven. You
set up the parameters of whatever
files you care to make. After
completing the setup the files are
dimensioned and you are ready to
go. The menu lists the number of
available files in the upper right
corner, so you always know how much
space is left.

You can call up the files by
any item in the file as well as by
number. Once a file is on the
screen, you can copy it to the
printer, continue searching for
another file with the same key, or
return to the menu.

One of the program's most in¬
teresting features is the "security
lock." It is a two-letter key to
enter the program. You must press
the code in order and at the right
interval to enter the program.
Without the code, you cannot enter
at all. If you have something to
keep confidential, this program is
for you.

I found the program tape balky
to load, but once finally loaded
and copied onto my own tapes, it is
easily retrievable. There is one
big note to make. The C-10 tapes
sent with the program are not long

$59«

95

64K MEMORY
M-64

129.95 WIRED & TESTED
IN STOCK. SAME DAY SHIPMENT
All Standard features included, plus lower 8K
of RAM can be disabled in 2K segments to
allow PROM or peripherals to be added.

EXPAND YOUR 16K SYSTEM

If you have a Sinclair 16K RAM module and need
more memory, expand it to 32K and beyond by using
BYTE-BACK M-16 MEMORY MODULES.

You can’t connect two Sinclair 16K RAM modules together,
but you can connect one Sinclair 16 K and one or more BYTE-
BACK 16K modules to get all the memory you need

THOUSANDS IN USE WITH PROVEN RELIABILITY

M-16 $59 .95 $69.95 wired and tested.

_ IN_STpCK. SAME DAY SHIPMENT

BB-1 Control Module, with S relays, 8 leds

& 8 inputs. $59 Kit. $69 wire and tested.
_ [N_SIOCK! SAME DAY SHIPMENT

ImODEM with RS232 Port. $99.^^ $ii995wire

*Kit

& tested.

90-Day Warranty On All Modules.
10-Day Return Privlledge
ORDER PHONE 803-532-5812

Add $4.95 shipping & handling to all orders.

BYTE-BACK CO. CHECKS

Rt. 3 Box 147 Brodie Rd.

LEESVILLE, SOUTH CAROLINA 29070

enough to record the program once
it is dimensioned. They will hold
12-13K, but not the full 16K.

Multifile can be listed and
modified. I made several small
changes in the program for some
specialized applications. My
favorite changed the menu to not
only tell you the files left open,
but to tell how many you used, how
many are left, and the total avail¬
able. This can be done by changing
only one line.

In summary, I found the program
useful for a variety of applica¬
tions. The security lock was a big
plus, and, since it can be listed
you can learn from the program as
well. It is well worth the invest¬
ment of $29.95.

Michael Roberts, Des Moines, lA

Our Multifile tape has 1 copy each
side. One loaded; one didn't.
Gladstone always replaces defective
tapes . — AZ

9

ZX8I

€0IT» ^ THEM M tO m

1 qI 2 am 3 am 4 q| 5 c

h Di

PLOT UNPLOT REM RUN RAND RETURN IF

INPUT POKE PRINT

ffif» OR* STEFW Cem OW W S V ^ .

QalWnlEEilRalTeilYfilu 1 1 lo IP

SIN COS TAN iNT RND STRS CHRS CODE PEEK TAB

NEW SAVE ; DIM FOR GOTO GOSU8 LOAD LIST LET

iPRIMT H SLOW j

ARCSfN ARCCOS ARCTAN SON A8S SOR VAL LEN USR

copy CLEAR CONT CLS SCROLL NEXT PAUSE BREAK

SHIFT

fz lx fc ’fv ^Ib In 1m"1 1

SPACE

Introducing the
Sinclair ZX81.

If you 're ever
going to buy a personal
computer, now is the time
to do it.

The Sinclair ZX81
is the most powerful, yet
easy-to-use computer
ever offered for any¬
where near the price:
only $99.95* completely assembled.

Don't let the price fool you. The ZX81 has
just about everything you could ask for in a per¬
sonal computer.

A breakthrough in personal computers.

The ZX81 is a major advance over the origi¬
nal Sinclair ZX80-the first personal computer to
break the price barrier at $200.

In fact, the ZX81 's 8K extended BASIC offers
features found only on computers costing two or
three times as much.

Just look at what you get:

■ Continuous display, including moving graphics

■ Multi-dimensional
string and numerical arrays

■ Mathematical and scien¬
tific functions accurate to
8 decimal places
■ Unique one-touch entry
of key words like PRINT,

RUN and LIST

■ Automatic syntax error
detection and easy editing

■ Randomize function
useful for both games and serious applications

■ 1 K of memory expandable to 16K

■ A comprehensive programming guide and
operating manual

The ZX81 is also very convenient to use. It
hooks up to any television set to produce a clear
32-column by 24-line display. It comes with a
comprehensive programming guide and oper¬
ating manual designed for both beginners and
experienced computer users. And you can use
a regular cassette recorder to store and
recall programs by name.

Sinclair technology is also available in Timex/Sinclair computers
under a license from Sinclair Research Ltd.

Order at no risk.**

We'll give you 10 days to try out the ZX81 . If
you're not completely satisfied, just return it to
Sinclair Research and we'll give you a full refund.

And if you have a problem with yourZXSI,
send it to Sinclair Research within 90 days and

These numbers are for orders only. If you just
want information, please write; Sinclair Research
Ltd., 2 Sinclair Plaza, Nashua, NH 03061.

*Plus shipping and handling. Price includes connectors for TV and cassette, AC adaptor, and
FREE manual.

* * Does not apply to 2X81 kits.

we'll repair or replace it at no charge.
Introducing the ZX81 kit.

If you really want to save money, and you
enjoy building electronic kits, you can order the
ZX81 in kit form for the incredible price of just
$79.95.* It's the same, full-featured computer,
only you put it together yourself. We'll send com¬
plete, easy-to-follow instructions on how you can
assemble your ZX81 in just a few hours. All you
have to supply is the soldering iron.

A leader in microelectronics.

The ZX81 represents the latest technology in
microelectronics. More than 10,000 are sold
every week. In fact, the ZX81 is the fastest selling
personal computer in the world.

We urge you to place your order for the
ZX81 today.

To order.

To order, simply call toll
free. Or use the coupon below.

Remember, you can try it for
10 days at no risk.** The sooner
you order, the sooner you can
start enjoying your own
computer.

Call toll free 800-543-3000.

Ask for operator #509.

In Ohio call: 800-582-1 364;
in Canada call: 513-729-4300.

Ask for operator #509. Phones
open 24 hours a day, 7 days
a week. Have your MasterCard
or VISA ready.

NEW SOFTWARE: Sinclair has 16K MEMORY MODULE: Like

published pre-recorded pro- any powerful, full fledged corn-
grams on cassettes for your puter, the ZX81 is expandable.
ZX81 . We're constantly coming Sinclair's 1 6K memory module
out with new programs, so we'll plugs right onto the back of
send you our latest software your ZX81 . Cost is $49.95, plus
catalog with your computer. shipping and handling.

Amount

Ad Code09SX0S

MAIL TO: Sinclair Research Ltd.,

One Sinclair Plaza, Nashua, NH 03061

Name.

Address.

11.5, dollars

ZX81 !

$99.95

ZX81 Kit

79.95

1 6K Memory Module

49.95

Shipping and Handling

4.95

total!

DEAR EDITOR

Brian O'Brien of Weston, MA,
suggested keeping the TV away from
the recorder to avoid picking up
the TV's 15KHZ noise. To lengthen
my SAVE and LOAD cables, I got two
36" long stereo cables with RCA
plugs at both ends. I clipped off
the plugs and added miniature
plugs. At 36" I have no more ISKHz
hum! The cables are shielded and
help prevent outside interference.
Be sure to solder the center core
of the cable to the center lug of
the miniature plug. I put black
electrical tape on one to distin¬
guish it from the other.

The female connectors inside
the computer are just not strong
enough to hold plugs firmly. When
you move cables, computer or recor¬
der, one or more of the plugs may
come out — usually the power plug!
Wind a tiny strip of masking tape
around plug bases. You'll need a
bit more pressure to get the plug
in and out. This is a cheap and
dirty alternative to replacing the
female connectors as Ron DeBalko
suggested (Jun.82).

Steve Schowiak, Hielbronn, Germany

I read with trepidation about
others' problems with system
crashes, TV interference, glitches,
overheated voltage regulators, ex¬
cessive line ripple and so on, but
I didn't expect every one of those
to appear at my doorstep the day my
ZX81 arrived. My solution was to
spend $19.95 to build a regulated
0-15V, 1.5 amp external power sup¬
ply, available in kit form from
Jameco Electronics, Belmont, CA
94002. I haven't had a glitch or
crash since and can run my ZX81
over 16 hours with stacked RAM
packs (for 32K) , even though cur¬
rent drain reaches 700-800 ma with
stacked RAMs. Try that with Sin¬
clair's power adapter! Jameco
gives exceptional service. In¬
stock items take less than 10 days.

even if you pay by personal check.

I cured the TV interference
by using ordinary coax TV cable
properly terminated with a 50 Ohm
resistor. I now hook up directly
into my TV through the 50 Ohm coax
connector, by-passing Sinclair's
antenna switch. Voila, a display
that is actually readable.

Joseph Dominiecki, Wisdom, MT

I hope no one got electrocuted
following Martin Oakes' suggestion
to connect their wrists directly to
earth ground in his Simple 4K-8K
ROM Switch (Jul.82 p.8). Static
damage is a real danger. However,
the human body acts like a 60 pico-
Farad capacitor for static electri¬
city and all that is needed is a
resistive path to ground to bleed
off static charge. Place a 200K-1
megohm resistor (1 watt carbon
comp — big for mechanical strength)
in series with the ground wire.
Likewise connect exposed metal or
conductive mats to earth ground
through the same or similar resis¬
tors to drain static charge without
shock hazard. A short stroll
across a carpet can build up 10000-
50000V charges on a body. When the
relative humidity is over 60%, this
charge dissipates slowly through
the air. When the RH drops below
30% the charge lingers. A 1 megohm
wristat drops that to 100V in
l/10th second or less. Field ef¬
fect devices (CMOS, J-FETS, MOS-
FETS) and some bipolar devices fail
with voltages (on 60 pF) as low as
100V. So protect that RAM or ROM,
but don't wipe out the user!

Dave Rogers, Santa Barbara, CA

Is it possible to merge sever¬
al utility programs from cassette
to ZX81? I'd like to load a renum¬
ber program and an input program
(replacing READ, DATA, RESTORE)
before entering a new program.

12

Ross Shuping, Greenville, NC

The Data-assette ZX99, reviewed
this issue, lets you do this. To
do it with software, check out
Siriusware's classified ad this
issue. — KO

Between the 8K ROM and the RAM
is 8K of "dead space." Is it pos¬
sible to put more RAM in that area,
or even an EPROM? Or does Sinclair
have other plans for this area?

Dave Straub, Petaluma, CA

Memotech's 64K RAM puts 8K in this
space. The CAI/0 board and Data-
assette's ZX99 use ROMs here, as do
a myriad of other manufacturers.

We know of no Sinclair plan to use
addresses 8K-16K on ZX81s. You can
place your own EPROMs in here.
Memotech plans to sell blank EPROMs
this fall (Aug. 82). — KO

As you know, there is a multi¬
tude of ZX81 software in all areas.
To choose among the array, I'd like
to suggest that manufacturers show
a screen display in their catalogs.
It's easier to visualize a program
with sample video.

Mark Rogstad, Wheaton, IL

I have a ZX81 with Memopak 64K
RAM. Normally, even with RAMTOP
and the machine stack at 65535, you
can enter only about 15K of BASIC
lines. Entering more lines causes
a crash when the top of the display
file (VARS minus 1) reaches 32768
(8000 hex). I found if I move the
entire display file beyond 8000h in
a single operation in FAST mode, I
can add another 16K of BASIC lines
for a total of about 31K.

You can do this easily with a
method like Frank O'Hara's (Aug.
82). Insert, say, a 2K-long dummy
REM line into a program containing
14-15K of BASIC. Once you have
added another 2K of your BASIC
program you can safely delete the
dummy REM line; as long as the
lower end of the display file

(D_FILE) does not drop below 8000h
during subsequent editing, the
system runs perfectly. In other
words, the display hardware can
handle the file when it is entirely
between 4000 and 8000h or between
8000 and C000h, but not when it is
partly in one block and partly in
the other. This trick doeb not
seem to work beyond 48K (C000h). I
don't know if other brands of 32K+
RAM will behave similarly.

When you have a long REM line
in a program, it's a good idea to
put another line of only a REM
right after it. Attempting to
delete the line immediately follow¬
ing one that is too long to fit on
the screen causes a system crash.

Peter Ulrich, New York, NY

After much frustration trying
to share my recorded programs with
a ZX81-toting friend, i discovered
the alignment of the recording head
of my Panasonic mini had gone
askew. It was merrily recording at
its own crazy angle, oblivious to
all that is universal and expected
of a machine of the eighties.

No problem to correct it — an
adjusting screw is generally vis¬
ible with the recorder in PLAY mode
and the tape door open. With a
small screwdriver, adjust the head
angle to give the loudest sharpest
sound when playing back a program.
This method may help coax an old
recorder into service.

Tom Gill, Milwaukee, WI

Last May 14, Bob Swann (and
later a voice named Carol) of CAI
Instrumemts promised to send me
detailed information about various
CAI products. It is 13 weeks since
my request — no info.

Ever hopeful, I ordered the
CAI/0 board and 40-column printer
June 7 with shipment promised in 4
weeks. Many weeks and calls to CAI
later, no printer and no word from
CAI. An order accepted is a con-

13

tract to deliver. I get only prom¬
ises and not performance. After
nine weeks and no cooperation, I
believe your readers deserve to
learn the truth about CAI and its
misrepresentations .

Christopher Bannister, Hopewell, NJ

Carol from CAI agreed that your
order was delayed beyond the origi¬
nal shipment date. This was be¬
cause of CAI's backlog replacing
Widgets with CAI/0 boards and 32-
column printers with 40-column
printers. CAI had problems meeting
manufacturing deadlines and have
hired another company to make their
products. Carol emphasized that
CAI does not make promises they
know they cannot keep; she recalls
saying she would try to get your
order out each time you called.

She added they are very aware of
their shipping problems and are
working to correct them. Your
printer went out UPS on 3 Aug. — AZ

We all have ordered software
and hardware from vendors inter¬
ested in collecting our money for
frequently shoddy merchandise who
hope they never hear from us again.
I found the opposite with CAI In¬
struments and Bob Swann. I pur¬
chased over a period of time both
the original 32-column printer and
the new 40-column printer. Being a
tyro in this field, I must have
called Bob a hundred times, fre¬
quently on weekends. I found him
extremely courteous, cooperative
and helpful in explaining to me the
arcane aspects of computer opera¬
tions. My last experience involved
a broken pin on the 20-pin plug
connecting the printer and CAI/0
board. Within 3 days of my call,
two replacement ribbons arrived.

If someone gives an award for best
equipment support in the field, I
will be happy to nominate CAI
Instruments and Bob Swann.

Peter Danes, New York, NY

USERS' GROUPS

Here's our latest list of ZX-TS
users' groups. To check for a
group in your area not listed here,
call or write us (please include a
self-addressed, stamped envelope)
and we'll tell you of any group
we know of. To list your group,
call or drop us a line and we'll
refer interested people to you.
SYNTAX, RD 2 Box 457, Harvard, MA
01451, 617/456-3661.— AZ

Santa Cruz, CA; Marc Reinig, High
Score Video Arcade, 2301 Mission
St., Santa Cruz, CA 95060.

Petaluma, CA; Michael & Susan
Degsive, 129 Saratoga, Petaluma, CA
94951.

Laguna Hills, CA: William H.

Brown, 5122 Brazo, Laguna Hills, CA
92653, 714/830-7628.

Provo, UT; Quint B. Randle, 255 N.
1600 West #76, Provo, UT 84601,
801/377-4757.

Lincoln, NE; Patrick Murphy, 4903
Walker, Lincoln, NE 68504, 402/464-
8086.

Kansas City, MO; Peter B. Wolcott,
305 W. 51st Terr., Kansas City, MO
64112, 816/753-8546.

Slidell, LA; Gulf Coast Sinclair
Users' Group, 144 Terry Dr.,
Slidell, LA 70458.

Nashville, TN; William Tracy, 3220
Lakeland Dr., Donelson, TN 37214,
615/889-6668.

St. Albans, WV; Sinclair Super
Group, William Meclow, 949 Brier
St., St. Albans, WV 25177.
Palatine, IL: Diana Wright, 2170
Oak Brook Cir., Palatine, IL 60067,
312/934-9375.

Milwaukee, WI; Bob Harris, 2604 N.
Murray #203, Milwaukee, WI 53211,
414/963-9675.

Newport News-Williamsburg-Hampton,

VA; Jim Langston, 146 Hawthorne
Dr^, Newport News, VA 23602,
804/877-3920.

Hopewell Jet., NY; Mid-Hudson
Users' Group, Fr. Bruce 0. Bowes,
Church of the Resurrection, Hope-
well Jet., NY 12533, 914/226-5727.

14

GLaOSTOnE- ^LECTROmCS GiaOSTOnE- -ELECTROmCS GLaOSTORE- -ELECTROmCS GLaOSTOnE-yELECTROniCS GLaOSTOnE-'i-ELECTROniCS GLaoSTORE- rELECTROmCS GiaOSTORE- -ELECTRORICS

with Quality Hardware and Software
from Gladstone Electronics

Cet serious a^ut ZXtti

& 15 loaa com^itiiw^

Cassette Software

DATA STORAGE SYSTEM

ZX81 Professional Keyboard
and Case

A full-sized professional keyboard for the ZX81 Features
47 keys and a full-sized space bar. Connects to the ZX81
with no soldering required, via a plug-in flexible connec¬
tor. You can purchase the keyboard only, or the optional
metal case that holds both keyboard and ZX81. Expan¬
sion devices (i.e. RAM packs, etc) connect to the ZX81
edge-connector which extends from the rear of the
cabinet.

A professional keyboard makes program entry easier
and less error-prone.

Keyboard (KB-1) . $85.00

Metal case for keyboard

and ZX81 (MC-1) . $25.00

PLUS

32KRAM

Machine Code Monitor and Disassembler

ZXBUG is a powerful tool for machine language pro¬
gramming. It is 4K long and uses memory from 71EO to
the top memory. ZX BUG works in hexa¬
decimal (base 16), not decimal, so all addresses are a
maximum of 4 Hex bits long. Provides a total of 28 com¬
mands.

Artie $14.95

ZX

A55EMBIER

Data Storage System

An amazingly versatile multi-purpose filing system for
the 16K ZX81. The program is menu-driven, and number,
size and headings of files are user-definable. Both string
and numerical files are catered for. Files may be
created, modified, replaced, and searched, and are pro¬
tected by an ingenious foolproof security system. Out¬
put to the ZX printer is aiso provided. The program
comes on cassette, together with three quality data
cassettes for file storage, and comprehensive documen¬
tation, describing a host of applications for both
business and personal use. Supplied in an attractive
storage case. If your ZX81 is bored with playing games,
then this program will give it plenty to think about!

with “piggy-back” feature

This Machine Code program occupies 7K of memory
and locates itself at the top of memory. The program is a
full Editor/Assembler and Monitor. Labels may be used
instead of any string. The features include Line Inser¬
tion/Delete, Insert Characters, Auto Repeat on all keys.
The monitor has facilities to inspect memory, registers
and run machine code programs.

Artie $14.95

A sensible choice for 16K RAM owners. Jigsaw 32K RAM
‘piggy-backs’ onto your 16K RAM to give a total memory
of 48K! If you do not own a 16K RAM, you may use a 32K
RAM instead. At a later date you may add the ZX81,
TS1000, or Jigsaw 16K RAM, should you decide you re¬
quire more memory.

A very useful, unique Jigsaw memory feature is the pilot
light showing if your ZX81 computer/memory is
powered.

Larger memory enables longer programs and greater
data bases, enhancing the value of your personal com¬
puter. And the Jigsaw 32K is parf of a fully compatible
ZX81 and TS1000 system of add-on products. Additional
exciting Jigsaw products to follow shortly!

The Complete ZX81
and TS1000 Library!

9 Powerful New Functions!

RENUMBER. This routine renumbers a program in any
step and from any line up to 9999
DELETE. This command deletes a group of lines in a pro¬
gram.

MEMORY. Prints how much spare memory is available.
DUMP. Displays current values of string and numerical
values, except arrays.

FIND. Will find any string of up to 255 characters and list
each line containing that string.

REPLACE. Replaces any string of up to 255 characters
by any other string.

SAVE. Transfers program in computer to below RAM-
TOP.

APPEND. Allows two programs to be joined.

REMKILL. Removes all REM statements from a program,
otherwise leaving it unchanged, preserving memory.

Artie $14.95

The Complete ZX81 Basic Course .

Basic Course Cassettes (2) .

Getting Acquainted with your ZX81 .

ZX81 Pocket Book .

Making the Most of Your ZX81 .

Computer for Kids, ZX81 Edition .

Explorers Guide to the ZX81 .

ZX81 Companion .

^9 Exploding Games for the ZX81 .

Not Cnly 30 Programs for ZX81 : IK .

Machine Language Made Simple for Sinclair

Mastering Machine Code on your ZX81 .

ZX81 Rom Disassembly: Part A .

ZX81 Rom Disassembly: Part B .

Understanding your ZX81 RDM .

Expands the ZX81’s memory capacity to its maximum.
Use instead of 16K RAM. Same features as other Jigsaw
memory products including pilot light and full com¬
patibility with other upcoming Jigsaw products.

Equivalent to ZX81 or TS1000 16K RAM. Fully compati¬
ble in appearance and performance with other Jigsaw
products.

CALL OR WRITE FOR FREE CATALOG

Call (716) 874-5510
For Visa, MC Orders

Mail order to 1585 Kenmore Ave. Buffalo N.Y. 14217 Checks or money orders. No CODs. Add shipping

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MATH FUNCTION EXECUTION TIME

Some calculations take longer
than others on my ZX81. I timed
each math function to get an idea
of which function to use when faced
with alternative methods of doing
the same calculation and to compare
the ZX81 with other computers.

Enter in FAST mode:

1 FOR 1=1 TO 1000

2 LET T=1

3 NEXT I

This program ran in 6.1 seconds
against a stopwatch. This is the
basic time to execute a FOR-NEXT
loop and assignment 1000 times.

I replaced the "1" in line 2
with each function in turn and
retimed the program. Deducting the
basic loop time gives the time to
do each function 1000 times. I
calculated the time in milliseconds
to perform each function once.

Execution times vary widely,
from 4/10000th second to one tenth
second. This means some methods of

calculation are better than others.
For integer powers up to 50 it is
faster to multiply out than use the
** function. It takes more memory
to multiply to get X**50, so there
is a trade off. Also it's faster
to use X*0.5 than X/2.

I tried using the loop variable
I in the calculations but it didn't
seem to affect the speed. This
leads me to assume that the times
in the table are valid for any num¬
bers used with the functions.

By comparison, most pocket cal¬
culators and pocket computers take
about 200 milliseconds per opera¬
tion. Typical minicomputers use a
few microseconds per operation.

Execution Times in milliseconds —
Z0X81 Math Functions

Function

Time

Function

Time

ABS 1

0.4

COS 1

40.6

SGN 1

0.6

EXP 1

41.3

INT 1

1.1

ARCTAN 1

60.9

1+1

1.2

LN 1

65.0

1*1

2.0

ARCSIN 1

69.9

1-1

2.1

ARCCOS 1

72.6

1/1

2.9

TAN 1

81.9

RND

11.9

1**1

105.4

SIN 1

39.1

SQR 1

106.4

Ron Charlton, Paducah, KY
SIGNIFICANT FIGURES SUBROUTINE — 8K

In scientific calculations the
accuracy of a computed value must
not exceed that of the least accur¬
ately known number used in the
computation. You can use the fol¬
lowing subroutine (at 1000 in this
program) in any program containing
the proper input, i.e., SF and Z,
to specify the number of signifi¬
cant figures in any expression.

Because the ZX81 holds 10**1,
10**2, etc., slightly inaccurately
(see part 2 of Dr. O'Hara's
article, Apr. 82), using QE=10**I
might give erroneous results. For
example, if SF=6 and
Z=0. 000098765432, using QE=10**10
would produce 0.000098765399. In

16

subroutine 1180, lEl through 1E13,
which are held exactly, are substi¬
tuted for 10**1 through 10**13.

For Z=0. 000098765432 and SF=6, this
gives the correct value,
0.0000987654, with the desired num¬
ber of significant figures. (Note
that the ZX81 will not print the
last significant figure if it is a
zero to the right of the decimal
point. It will, however, be
counted as a significant figure
by the subroutine.)

Use this subroutine as often as
necessary by repeating the GOSUB
command after assigning each new
value to Z. The ZX81 can handle up
to eight significant figures.

N. Handshaw Clark, Bryan, TX

10 REH "RNY PROGRRH"

20 PRINT "HOW MRNY 5IGNIF1CRNT
FIGURES DO YOU WISH?"

30 INPUT SF
4.0 CLS

"^INPUT NUMBER:"

60 INPUT Z
70 CLS

S0 GOSUB 1000
90 PRINT 2
100 STOP

nil pEM_^"SIGNlFICfiNT FIGURES"

X0S@ LET I=SF
X030 GOSUB 1180
1040 LET ESF=OE

lie® Z>=<ESFi THEN GOTO 1

1060 FOR I=s0 TO 30
1070 GOSUB 1180

U = 1NT C (RBS Z4- (@.5^0E) )

1090 IF W< (ESF^.'lEl) THEN NEXT T

lifi "

lia© FOR 1=0 TO 30
1130 GOSUB 1180

3^0E? W = INT ((BBS Z.|-(0.S«OE) )

>>>= tESF) THEN NEXT 1

lilt hiruiS

1180 LET ©E=1©»»I
1190 IF 1=1 THEN LET OE=lEl
120© IF 1=2 THEN LET OE=lE2

1=9 THEN LET OE=lE3

1220 IF 1=4 THEN LET OE=lE4

1230 IF 1=5 THEN LET OE=lE5

lg’40 IF 1=6 THEN LET OE = lE6

1-26© IF 1=7 THEN LET OE = lE7

1260 IF 1=8 THEN LET OE=lE8
"^HEN let OE = lEi
1280 IF 1=10 THEN LET OE=1E10

III® 1=11 then let oe=ieii

13®® 1=12 THEN LET OE=lEia

iiil RETu5n= OC.1E13

SYNTRCTIC SUM: 6© 191^ 8K

SYNTAX ERRORS: In Jason Harper's
Printing on the Bottom Line (Aug.
82), line 60 of the second program
should read: 60 POKE 16418,2

John Oliger of Indianapolis
wrote of the battery back-up proj¬
ect Aug. 82: "Mr. Nachbaur refers to
part nos. LM340T-5 and 78L05 for
the regulator in this circuit. A
78L05 would never work. He should
have said a 7805. A 78L05 (in a
TO-92 or TO-39 package) is only
good for lOOma max. The 7805 is a
1 amp regulator and the LM340T-05
is a 1.5 amp regulator. Both are
in the TO-220 package."

Fred Nachbaur wrote that in
Fig. 2, same article, the arrow
identifying the emitter lead of Q1
should be in the top "leg," point¬
ing toward the transistor base sym¬
bol. Also, Syncware cut R1 to 62
Ohms, reducing battery warmup after
extended use by decreasing battery
charging current. It increases re¬
charge time to about 24 hours — no
problem if the unit is just a back¬
up. Higher values (75 or 81 Ohms)
work but increase recharge times.

PROGRAM IMPROVEMENTS/REFINEMENTS

To polish Harold Miller's MC screen
fill program (Aug. 82) , change JPNZ
at 16522 and 16526 to JRNZs. Since
JRNZs are 2 bytes long, the line is
just 14 bytes. The same line can
fill the screen with different
characters from different places
in a program without changing the
JPNZ addresses. The basic line
reads in hex:

3E 80 06 04 OE BO D7

OD 20 FC 05 20 F7 C9
USR 16514 blackens the screen. If
you put 3E 88 18 02 in front of
this line, USR 16514 gives a gray
screen; USR 16518 a black one. Add
any number of 4-byte changes to the
front of the line. Increase the
code of the 4th byte by 4 for each
set and increment USR calls by 4
for each new character fill.

17

Robert A. Foley, Umatilla, FL

The Sinclair ZX81 personal computer kit

AD CODE
09SX0K

Imagine building your own computer
for only $79.95!

That’s exactly what you can do with
the ZX81 kit. It comes with all the parts
you need and complete diagrams and in¬
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and a screwdriver. Plus, of course, a little
bit of work.

But you get a lot more than several
hours of kit-building fun. You also get a
surprisingly powerful personal computer.
The ZX81 hooks up to any TV for a 32-
character by 24-line display (we provide
the connecting cables). You can also use a
standard cassette recorder to store your
programs (again, we provide the cables).

Most important, you get a BASIC pro¬
gramming language that’s powerful
enough to challenge and interest the
most experienced pro^ammers. The
ZX81 can handle multidimensional string
and numerical arrays. It has full mathe¬
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command. Syntax error detection, de¬
bugging codes, and easy editing. Plus
features that are ideal for creating games,
such as 20 graphic symbols, continuous

display, and random number generator.

The ZX81 can be expanded too. You
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with our Memory Module for $49.95.

And you get a comprehensive manual
that completely documents the capabili¬
ties of the ZX81, and teaches program¬
ming from the ground up.

In short, you get all the features that
have made the Sinclair ZX81 the fastest
selling personal computer in the world.
And you get the satisfaction and fun of
building it yourself.

A few years ago, this kind of computer
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But the ZX81 kit can be yours for only
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Ask for operator #509. Phones open
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These numbers are for orders only. If
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MAIL TO: Sinclair Research Ltd., 1

One Sinclair Plaza, Nasjiua, NH 03061. I

PRICE* QTY. AMOUNT

ZX81 Kit

16K Memory
Module

Shipping and
Handling

*U.S. dollars

TOTAL

Sinclair technology is also available in Timex/Sinclair
computers under a license from Sinclair Research Ltd.

Name

Address

inczlaii—

MACHINE CODE PROGRAMMING—

#9: TESTING BITS FOR BRANCHING

You can test any bit in any
address simply by loading a regis¬
ter and choosing the right instruc¬
tion code. This facility is fairly
easy to understand and can be used
even in very short machine code
(MC) subroutines.

For example, if you have a
block of data with both positive
and negative values less than 128,
you can use the instruction BIT 7, A
after loading A with a value. If A
is positive, the Z Flag will be set
to 1; if A is negative, the Z flag
will be reset to 0. Then a Test-
and-Branch (T&B) can give the value
to the correct area for processing.

How does this instruction work?
The 7th bit in A, either 0 or 1,

"+" or is "inverted" and put

into the Z bit of the Flags regis¬
ter. If your T&B is JR Z and the
7th bit of A is 0, then Z will be 0
and control will not jump. Remem¬
ber that a Flag is "true" if equal
to 1, or "set".

Another example: suppose you
have a block of data with odd and
even values less than 256, and
you want the addresses of the odd
values. One solution is to set up
a loop with HL. (Odd values will
have a 1 in bit 0; even values will
have a 0 in bit 0.)

The possibilities are endless,
so here are some general rules:

1. Select the proper instruction.
If the address is important, use
BIT n,{HL). If the value is
important, use BIT n, register.

2. First, load the proper register
(or HL pair) with the value (or
address) , then test the bit.

3. Follow the bit test with a
Test-and-Branch instruction with
two possibilities:

A; Bit test fails — continue
search loop (Ex. JR Z ;Z=0)

B: Bit test succeeds — Branch

to processing area (Z=l) (or. A:

JR NZ for branch and B: Continue
search loop.)

4. If your data block is used more
than once per USR-call, then add a
"trigger" value into the last data
address for a "value" Test-and-
Branch to an area for resetting the
address-pointer .

Next month: JUMPING AROUND

Jon Bobst, Zeta Software, PO Box
3522, Greenville, SC 29608-3522

HARDWARE REVIEW

Product: ZX99 Tape Control

System

From: Data-assette, 52 S. 3rd

St., Oxford, PA 19363,
215/932-3626.

Price: $150 (includes cables)

Don't be fooled by the name.
This is a tape operating system.

And a good one.

Data-assette's ZX99 Automatic
Tape Control System can read and
write records (called blocks) that
let you keep data files separate
from programs. You can read in two
program tapes, concatenate them and
write out a new program tape. You
can generate blocks containing only
single values or read a 4K tape
into a string and write a program
to automatically translate it to
8K. In short, you can have most
disc functions at low cost.

The hardware is well built;
the manual is not. It took me some
time to understand that I had to
operate the recorders manually in
the LOAD and SAVE modes. Selecting
recorders turns them on before you
can type the LOAD or SAVE commands,
unless you stop them by hand before
selection. This mode bypasses ZX99
control and puts you in the normal
TS computer mode.

Unless your programs RUN auto¬
matically and reset the ZX99, your
control program can't LOAD and then
stop the recorder — LOADing wipes
the control program.

When using the ZX99, you can't
use other boards using addresses

19

8192-16383. You must configure
Memotech 64K to select neither the
8-12K nor the 12-16K block; nor can
you use printer interfaces with
these adresses. This flaw results
from incomplete decoding of the
ZX99's 2K ROM addresses.

ZX80 owners must work out how
to add ROM CS to pin 23B of their
machines to use a ZX99.

We tested most ZX99 functions
and found them reliable. We ran
into some problems caused by (we
think) a loose connection. Check
the setup carefully: problems show
up as oscillations on the recorded
tapes, making them unuseable.

Additional memory setups tried
created high-frequency noise in the
quiet spot on the tape. Sinclair's
16K RAM couldn't write a tape that
reloaded — the hash was too loud.

Our Memotech 64K and TS1016 made
noisy but usable tapes. Our IK
machine produced quiet tapes.

Cables supplied with the sys¬
tem connect the recorders and your
computer cables connect the ZX99.
You must make your own printer
cable to connect a 3.5mm plug and a
connector to match your printer.

Listing to a serial printer
via the RS232 port is very simple.
Define a value (Y) that programs
the interface, then call USR 8225
to start the listing. Lines will
be your printer's maximum width or
60 columns, whatever comes first.
Lines ending in keywords extend
past the margin to complete the
keyword, but not its argument. You
can't create a screen format in the
LIST mode. Extra blank lines follow
GOTO, STOP or RETURN as an aid.

In BLOCK PRINT mode, a shifted
T prints the TS "<>" character
which generates a carriage return
and line feed for your printer.

In either mode you get full
128 character ASCII output. You
can't send from a terminal to the
computer. Baud rates from 110 to
9600 are available under software
control. Handshaking isn't avail¬
able, but you can choose even or

odd parity generation. A simple
choice in software exchanges the
relation of caps and lower case to
normal and inverse video.

On our printer (a CDI 1205
terminal) print lines were right-
justified in the buffer if "<>"
used for CR/LF was at the end of
the line. Under these circum¬
stances the right margin wandered
about three characters. When LF/CR
is at the start of the print line
we get left- justified text and
stable margins. The 47-page manual
failed to explain this and it took
several hours to learn.

Data-assette told us a minor
ROM bug was found and all early
buyers got free upgrades.

Despite its limitations, this
is a powerful add-on to your ZX/TS.
Syntax has seen no other program
development aids that allow this
level of flexibilty. — KO

CLASSIFIED ADS

Reach thousands of ZX80/81 owners!
Send your ad, typed 35 char/line,
with check to arrive by the 15th of
any month for the next month's
issue. Ads arriving after the 15th
appear in the issue following the
next unless you request its return.
Ads are $9 per line and must be
resubmitted for each month. No
phone orders or credit cards. We
take no responsibility for adver¬
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2 Box 457, Harvard, MA 01451.

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1981&82 NFL stats at your command! I
Exc display by team, division, &more!
Update 1982 stats with weekly entry
Hurry!The season is about to begin!
16K,ZX81 Tape $9.95 Money Orders
sent same day. ZAMIS ENGINEERING
251 First St., Perrysburg, OH 43551

SYNTAX offers a faster way to find
answers! NEW Laminated Micro¬
processor Instant Reference Cards
Z80,6502, 8080A & 8085A, 8048 &
relatives, and programmers'

20

algorithms ref. card, $5.95 each.
Prices include shipping. SYNTAX RD
2 Box 457, Harvard, MA 01451.

**********THE FUNWARE CO. **********
l.LAND THE SPACE SHUTTLE 2. LAND/AIR
BATTLE 3. SPACE BATTLE 4.HUNTMAN*ALL
ZX-81/16KRAM ON QUALITY C-20 TAPES,
each game $4.95 or all four $16.95.
PAPER FOR ZX/PRINTER $6.50 PER ROLL
All prices include shipping/handle.
7119 Santa Fe Av. Dallas, Tx. 75223

BRAINWAVES & ZX81 CONTROLS MUSIC
speech, robots. News & catalog $3.
Rosetronix 269 Dahlia I.B.CA. 92032

Software for all Sinclair Computers
WRITE FOR OUR FREE CATALOG & CODING
& DISPLAY SHEETS : Lamo-Lem Labs, Code
115, Box 2382, La Jolla, CA 92038.

PARENTS/TEACHERS — 4 pgms for pre¬
schoolers and spec. ed. students.
Develop beg. reading skills. Large
letters, rewarding graphics. Cass¬
ette for ZX-81,16K. $20ppd. SCREEN-
MAKERS, 351 Badger, Guffey, CO80820

<*VOTEM*> Analog Interface* Measure
voltage & temperature with your ZX*
$39 .95/kit-$59 . 95/asm-$5/doc alone*
Add $3/USpost* Down East Computers*
PO Box 3096A, Greenville, NC 27834 *

Finally, a GRAPHICS DUNGEON FAN¬
TASY GAME . Treasure Seeker . find
booty & fight monsters. Plus: MARS
LANDER, SKIIER, CRUMBLIN CAVERNS.
All on tape for $6.95. Send money
tozSpartan Software, 1403 Gloria,
Boulder City, NV 89005 (8K/16K)

On cassette; 3 new game programs
for the 16K ZX81; $6.00;OCH Jr.

RT. 3, BOX 229, AMITE LA70422

DRY GULCH. An interactive adventure
written in the classic style. Over
100 words of vocabulary. This one
will take days to solve. Written
in BASIC, it is listable and may be
SAVEd in progress. 8K/16K. Send
$10 for a cassette to; UPSTATE LABS
27 ELVIRA STREET ROCHESTER, NY 14606

EVEN BETTER THAN BEFORE!

TH£ SINCLAIR COMPUTER FAMILY SOURCE
BOOK (1st Revision) lists over 600
programs, books, & accessories from
over 80 suppliers. Only $6.95+$1.25
P&H. VA res. add 4%. Send check or
Money order to ATLANTIC COMPUTER
PRODUCTS, POB 936 Norfolk, VA 23501
***********************************

"COIN COLLECTION" Menu format;
add/delete, check inventory , change
cost/value, total cost/ value, search,
auto-run/auto-save & morelListable.
8K ROM,16K RAM. Tape+manual $10.95
"UNIVERSAL INVENTORY FILE" You
create the file headings. Menu and
prompts. Two ways to search, add/
delete, check&more! 8K ROM, 16K RAM.
Tape+manual $16.95. M.C. Hoffman Co.
P.O. Box 117, Oakland, N.J. 07436

UTILITIES FOR SERIOUS PROGRAMMERS
— R/W(8K/2K) Data tape read/write
(can also read SAVEd tapes as data)
— MRG(8K/16K to be useful) BASIC
save/merge/erase (combine in-RAM +
taped BASIC) . Self-load ML cass -
ZX81/TS1000. R/W only $10; both for
$15. SASE for info. SIRIUSWARE
6 Turning Mill Lexington MA 02173

POWERSUPPLY REPLACEMENT WALL PLUGIN
For ZX81 handles lK,16K,32K,and 64K
RAM. Won't overheat or lose memory
under continuous or intermittent
duty. Send check or MO for$19.95 to;
D&B Power 204 N. Fehr Way Bayshore
NY 11706 Dept G. Includes P&H
NY res. ADD sales tax Fast delivery

PRESCHOOLERS have fun and learn on
SCREENMAKERS readiness programs.
Write 351 Badger, Guffey ,0080820

Engineers , contractor s-design prog¬
rams written by PE; H/AC load, duct,
plumb. , sprinkler .Free cat-P Symonds
1345 Dewey Ct., Rockledge, FL 32955

Kit to solve ZX81 heat dissipation
problem. INSTALLS IN SECONDS. Send
3.95 chk/mo to: R.H.,Inc. 7683
Thompson Rd. Cincinnati, Ohio 45247

21

AIRPLANE FLIGHT SIMULATOR. RADIOS (2
chans) : VOR,DME,ADF,Glideslope. Map
display shows position (movable) .
Multi-leg trip ends with instrument
landing. Inst ructions. Cassette for
ZX81/16K. Send $9.95 check or money
order to: AMANDA SYSTEMS,

P.O.Box 118, Holmdel,NJ 07733

BASE CONVERSION for ZX-81 w/16k.
Great machine language aid! Tape
$5.00. Maracomp,1525 N. Euclid
#122, Tucson, Az. 85719

>>>>> STUART SOFTWARE PRESENTS <<<<

> <

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> <

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> Football league games-Complete <

> with point spreads. Only $9.95. <

> Order from; STUART SOFTWARE <

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> 8K/16KRAM SUITE 316 <

> LAGUNA HILLS, CA92653<

> Enclose $1.50 shipping/handling <

LOADING PROBLEMS? — Our cassette
interface works! Complete systems,
29.95; 39.95 w/led indicator. Over
20 PROGRAMS AVAILABLE! SASE to:
Phoenix Engineering Systems, 4240
Lakeshore, Deckerville, Mi. 48427

"EPHEMERIS V" (c) for the 16K ZX-81
Merc., Venus, Mars, Jup. & Sat. all
found w this 16K prog. NO CALCULA¬
TIONS. Any date, time and place on
Earth. Graphic disp. in, and loc of
current constell. in simple terms.
PLUS r.a. & dec. & LOCAL side, time
For this amazing tape send $8 to:
Ephemeris V, 124 Professional Ave.
P.O. Box 261, Winchester, KY 40391

COMPUSETTE is a C-10 cassette which
is especially designed for micro¬
computer application by TAPEMASTERS
25 for $20.00 100 for $70.00

VISA MASTERCARD C.O.D.

TX 214-349-0081**OTHER 800-527-1227
10% Discount for Check with Order
P.O. Box 38651*Dallas , Texas 75238
FREIGHT PREPAID*DEFEGTIVES REPLACED

MONKEY BARRELS for IK ZX81! Climb .
bldg, jump barrels or die! Listing
$2. PANERO SOFTWARE, 3309 Lewis,
Long Beach, Ca. 90807. Exciting!!

FIFTY NIFTY PROGRAMS FOR YOUR ZX81!
Book has 50 Top Quality IK programs
w/instructions+comments . Plenty of
GAMES/GRAPHICS/FUNSTUFF. ONLY $9.95
LEE CARTER Bx 246 Harrison, ME 04040

RAMPAK OWNERS. DECODER fits inside
ZX80/81 and remaps internal ram to
8-9(10)K. $5.95pp-USA. JOHNOLIGER
10115 Nassau Ln. Indpls. In. 46229

m LI STABLE PROGRAMS ON 1 CASSETTE"
Mastermind , Doublemind , Slot Machine ,
Craps ,TicTacToe , Sub Rescue , Whit eHot
Number. NEW ENGLAND SOFTWARE, Box 691
Hyannis,MA 02601 . lK-$7 . 95 , 16K-$9 . 95

** SALE -ZX81 CONNECTOR $4.85,5/$23
2K RAM$12,0-16 PORTl/0 w/KEYBOARD
PLANS $5, ADD 50 t PER CONNECTOR P&H
POWERTRONIX 25E23 Bayonne, NJ 07002

CREATE OUR OWN GAMES-10 IK programs
reveal moving graphics techniques-
tanks ,D&D , Bombs &mor e-Lis tings$2
Q&M Pub. 225N. 1600W.#76Provo,UT84601

16K-"ZX81 MONOPOLY"or "TRADER JACK"
Monopoly in Spanish, Amer or Britain
Trader Jack in South Pacific
SAVAGE SOFTWARE- SW IMPORTERS
PO BOX 441 TITUSVILLE, FL 32780

ARTIST is a 8K/16K program that,
with more than 25 commands, helps
create drawings/paintings on screen
Features include: user's choice of
brushes and backgrounds, free mix
of graphics and alphanumer ics , easy
specification of lines and circles,
ability to store and recreate com¬
plex patterns by defining new
commands, and to save the artwork
on tape or print it. $10. KSOFT,

845 Wellner, Naperville, Ill 60540

Z-SHIRT says ZX COMPUTER POWER. Top
quality shirt. Kids (SML) or Adult
(SMLXL) . Specify. $8.50ppd SCREEN-
MAKERS, 351 Badger, Guffey, CO 80820

22

NEW ZX81 heatsink eliminates system
crashes due to overheating SASE to:
B Sanzone 289 Baxter La Milford CT

CENTRONICS SYTLE PRINTER INTERFACE*
for typing labels, forms, letters, or
program results. Large or small
letters or Graphics using GP-100A
printer. Board $45, cable $22.50.
Professional Electronics ,109 Ches
ney Lane, Columbia, S.C. 29209 _

OUR POLICY ON CONTRIBUTED MATERIAL

SYNTAX invites you to express opinions related to any Sinclair computer or
peripheral, or the newsletter. We will print, as space allows, letters discussing items
of general interest. Of course, we reserve the ri^t to edit letters to a suitable length
and to refuse publication of any material.

We welcome program listings for all levels of expertise and written in either
Sinclair BASIC or Z80 machine code. Programs can be for any fun or useful
purpose. We will test run each one before publishing it, but we will not debug
programs; please send only workable listings. Programs submitted on cassette can be
tested more quickly and with less chance of error.

In return for your listing, we will pay you a token fee of $2.00 per program we
use. This payment gives us the nonexclusive right to use that program in any form,
world-wide. This means you can still use it, sell it, or give it away, and so can we.

We will consider submissions of news and hardware or software reviews. Please
keep articles short (350-400 words). Again, we reserve the right to edit accepted
articles to a suitable length. We will pay 7 cents per 6 characters, including spaces
and punctuation, for accepted articles.

When you send in programs for possible publication in SYNTAX, please
include the following information:

• How to operate the program, including what to input if it does not contain
prompts.

• Whether you can run the program over again and how.

• How to exit the program.

• The Syntactic Sum (program published in Feb. 81 and Jun. 81; send SASE
for a free copy).

• What RAM size program requires.

• What ROM program uses.

We pay for this explanatory text at the same rate as for articles in addition to
payment for the program itself.

If you want us to return your original program listing or article, please include
a self-addressed, stamp>ed envelope. Otherwise, we cannot return submitted material.

PII2 THAT SINCLAIR TQ WORK! 1
ZX Phone Book 16K. Holds 720 fully
editable names! Very useful index/
cataloging tool. List/notes. . .$4.95
Tom Woods Box 64 Jefferson, NH 03583

SPECIAL3PROGRAMSZX81SEND$H-SASE
to PO Box 3073 San Jose,CA 95156

AMATEUR RADIO LISTS 16K DXCC & QSL
Manager Both $4.95 Pierce Co. Box
131 Derby KS 67037

CURVE FIT PGMS/ZX81 IK $10. 00/John
Anunti,3309 20th, San Fran. ,CA94110

12" B&W video monitor only $89.95.
Includes plans and kit for direct
video modificatin of ZX81. Random
Access box 41770S Phoenix, AZ 85080

BUFFERED BUSS/DEVELOPMENT BOARD for
ZX80/81: $40=BARE BOARD, $65=KIT.
UHF modulator $15. Connectors $6.
ZX81 REPAIRS $20+parts. Send for
details. COMPUTER CONTINUUM 301-16AV
San Francisco, CA. 94118. (415) 5243730

ZX81 ASSEMBLER & ZX81 DISASSEMBLER
on cassette $15. for info, send SASE
SERIAL PRINTER interface (thru MIC
port) plans & listing $5. Bob

Berch 19 Jaques Rochester NY 14620

SYNTAX is published

monthly by a wholly-owned
subsidiary of The Harvard Group.

Syntax ZX80, Inc.

RD 2, Box 457, Harvard, MA 01451.

Telephone 617/456-3661.

12 issues, $29. Single issue, $4.

Publisher: Kirtland H. Olson
Editor: Ann L. Zevnik

© Syntax ZX80, Inc., 1982. All
rights reserved. Photocopying
prohibited. ISSN 0273-2696

YES! Please send me 12 issues of SYNTAX for $29.

□ My check for $29 is enclosed. □ Please charge my □ MasterCard
Make checks payable to: □ Diner’s Club □ American Express

SYNTAX ZX80, INC. □ VISA □ Carte Blanche account

account number _ _ _

exD. date

bank number fMC onlv)

signature

Name

Title

Organization

City

State Zip

Dav Phone (

)

Evening Phone ( )

9 8?

I own a □ Sinclair ZX80

□ Sinclair ZX81 Telephone orders call

617-456-3661

23

EZRA GROUP II
EZRA GROUP II

LOW LOW LOW LOW LOW LOW LOW LOW LOW

PRICES!

Biorhythms 8K ROM/lK&up . 1.00

Graphics billboard 8/lup . 1.00

Horse Race 8/lup . 2.00

SPINNER TM(like Rubik ' s) 8/16 . . . 2 . 00

Improved SLOW PAUSE . 1.00

Linear Regression 8/lup . 2.00

CHAR. Generator Demos 8/lup. . . . 2 . 95
TAP WRITER TM (Handicap Aid) 8/1. free

SPLIT-A-STACK TM SLOW/lup . 2.00

CHEWTER TM(like PACMN) SLOW/lup. 2 . 95

ISLAND SQUARES TM SLOW/2up . 2.00

Random MUSIC ! SLOW/lUP . 2.00

BASIC keyword Demos 8/1.... from .50
ORDER, SASE, reSASE gets you GOO¬
DIES Catalog and MFREEI! Program
EZRA GROUP II
EZRA GROUP II

POB 5222 San Diego, California 92105

**ADD MEMORY THAT WON'T FORGET ! ! **

* Complete kit; $31:90 incl.s&h *
Full details w/stamp; HUNTER 1630

* Forest Hills, Okemos MI 48864 *

***MECHANICAL DESIGN PROGRAMS***
Programs provide tested solutions
expandable ideas & solutions of
Machine design problems. Send
$5.00 for sample programs to,

M.R. MADIGAN 295 Westview Ave.
Wadsworth, Ohio 44281

Tl-E

H\RV\RD

GROLP

Bolton Road. Harvard, Mass. 01451

Speed it up! Your programming that
is! Non-Trivial Solutions' ZXPRESS
IntegerBasicCompilerCompiles ZX-
81 source code to machine language.
This means your programs can be de¬
bugged rapidly in Zx-81 BASIC, then
stored in REM statements or in
2000H to 3FFFH address segment, if
available. The ZXPRESS Compiler
will make your ZX-81 20 to 50 times
faster. It's variables are 16 bit
two's complement integers. The com
piler allows multiple statements/
line. With the ZXPRESS the source
code can be located anywhere and
the position of the compiled code
write a long program, compile it in
pieces, then assemble the pieces.
The ZXPRESS is available from N-TS
for only $29.95. For mind stimu¬
lating recreation, N-TS continues
to offer the games Letter Raiders
and Life with Palette for $9.95
each. NON-TRIVIAL SOLUTIONS, P.O.
Box 2941, Amarillo, TX 79105, 806/

376-5723. Check, MC, Visa welcome.
***********************************

***********************************

♦CUSTOM ATTACHE CASE Formfit for *
*ZX80/81,TS 1000 and hardware for *
♦info send SASE COMPUTA-DEK 6009 ♦

♦Kenwood Dr. Nashville, Tn. 37215 ♦
***********************************

U.S. Postage

First Class Harvard, MA

Permit No. 8
01451